1. Technical Field of the Invention
In the examination of patterns such as the wiring patterns of semiconductors, printed circuit boards, liquid crystals, or plasma display panels etc or printed/impressed patterns, the present invention relates to a method of detecting pattern defects whereby defects are classified and detected.
2. Description of Related Art
Conventional methods of detecting pattern defects include the design rule check (DRC) method and the comparison method. The DRC method involves detecting the pattern line width and pattern separation by image processing. If the detected line width or pattern separation as respectively shown in FIG. 16A and FIG. 16B is not in accordance with certain wiring or pattern rules, such is determined as a pattern defect. In the example shown in FIGS. 16A and 16B, the line width and the pattern separation are both smaller than predetermined values, and therefore are detected as failures. The comparison method involves comparing a subject image S that is input with the previously registered image of a good product G, and detecting the difference of these as a defect pattern D, as shown in FIG. 17.
However, with the DRC method, as long as the detected line width or pattern separation satisfies certain rules, the pattern is determined normal. For example, in such a case as shown in FIGS. 18A and 18B, a bridge or a slit in the pattern cannot be detected as defects. On the other hand, normal patterns may be detected as failures if they contravene the pattern rules. For example, the separation P shown in FIG. 19A or the line width Q shown in FIG. 19B may be detected as a pattern defect.
With the comparison method, minute differences between the subject image and the registered image of a good product cannot be distinguished from noise etc, and so minute defects cannot be detected. Moreover, crucial defects such as a bridge D2 shown in FIG. 20 cannot be differentiated from permissible defects such as protuberance D1 shown in FIG. 20.
In view of the above, an object of the present invention is to provide a method of detecting pattern defects that is capable of classifying and reliably detecting various pattern defects.
A method of detecting pattern defects according to the resent invention involves comparing an input subject pattern with a good product pattern that is registered beforehand, in which a different portion of the good product pattern and subject pattern is detected as a defect pattern, and the defect pattern is classified and detected in accordance with the features of the contour of the defect pattern. Pattern defects of various types such as for example bridges, breaks, residual patterns, missing patterns, projection/protrusion, nicks/intrusion etc can reliably be detected and classified.